Drawing head for a drawing machine

Abstract

A drawing head for a drawing machine has a base plate with a central bore.he base plate is nonrotatably attached to the drawing machine. A rotatable straightedge support under the base plate has a central pin extending through the central bore. A nonrotatable cover plate is mounted on the pin with a gripping knob above the base plate. A spacing ring is rotatably positioned between the base plate and the cover plate. Locking devices are provided for releasably retaining the straightedge support with respect to the spacing ring and for releasably retaining the spacing ring with respect to the base plate. It is thereby possible to reduce the overall height of the drawing head while maintaining the bearing precision, and to thus achieve lower costs for production and assembly of the drawing head. Bearing means are provided whereby the central pin which engages the bore of the base plate is axially supported and rotatably positioned therein to firmly support the spacing ring. Moreover, the straightedge support is axially supported and rotatably positioned on the bearing means.

What is claimed is: 
     
       1. A drawing head: a base plate adapted to be attached to the drawing machine, the base plate having a central bore;   a straightedge support adjacent to the base plate and rotatable with respect to the base plate;   a central pin which extends through the central bore and being operatively connected with the straightedge support;   a cover plate attached to the pin;   a gripping handle attached to the pin and projecting above the cover plate;   a spacing ring rotatably mounted between the base plate and the cover plate;   first locking means for releasably retaining the straightedge support with respect to the spacing ring;   second locking means for releasably retaining the spacing ring with respect to the base plate; and   bearing means which are rotatably surrounding the central pin and which are rotatably mounted in the bore of the base plate and which are rotatable with the spacing ring, the straightedge support being axially supported and rotatably positioned on the bearing means.   
     
     
       2. A drawing head as set forth in claim 1, comprising in addition: a thrust element which is axially supported on the bearing means and which extends radially outwardly between the base plate and straightedge support.   
     
     
       3. A drawing head as set forth in claim 1, wherein the bearing means includes a disc assembly comprising a top thrust disc, a first bearing disc positioned in the base plate and having substantially the same thickness as the base plate, an intermediate thrust disc, a second bearing disc positioned in the straightedge support and having substantially the same thickness as the straightedge support, and a bottom thrust disc. 
     
     
       4. A drawing head as set forth in claim 3, wherein the first locking means comprises a first bearing disc having at least one locking slot on its circumference and a locking element is provided in the plane of the base plate which releasably engages the locking slot to fix the bearing means and spacing ring with respect to the base plate. 
     
     
       5. A drawing head as set forth in claim 3, wherein the second locking means comprises a second bearing disc having at least one locking slot on its circumference, and a locking element is positioned in the plane of the straightedge support which releasably engages the locking slot to fix the straightedge support with respect to the bearing means and the spacing ring. 
     
     
       6. A drawing head as set forth in claim 3, wherein the straightedge support and the base plate have substantially the same thickness and the same inner diameter, and the first and second bearing discs have substantially the same thickness and the same outer diameter. 
     
     
       7. A drawing head as set forth in claim 3, wherein the spacing ring is formed as a unitary piece with top thrust disc. 
     
     
       8. A drawing head as set forth in claim 1, wherein the spacing ring is connected with the bearing means. 
     
     
       9. A drawing head as set forth in claim 1, wherein the bearing means includes a first braking means comprising a first braking disc of thin metal which is used for retaining the base plate relative to the bearing means and the spaceing ring, and a first brake shoe which presses the first braking disc against the base plate. 
     
     
       10. A drawing head as set forth in claim 9, wherein the first braking disc is located between the first bearing disc and the intermediate thrust disc. 
     
     
       11. A drawing head as set forth in claim 9, wherein the bearing means has second braking means comprising a second braking disc for retaining the straightedge support relative to the bearing means and the spacing ring, and a second brake shoe which presses the second braking disc against the straightedge support. 
     
     
       12. A drawing head as set forth in claim 9, wherein the first brake shoe is displaceably mounted substantially parallel to the bearing axis and the top thrust disc has a thickness such that the spacing between the spacing ring and the base plate radially outwardly of the thrust disc is sufficient to accommodate the first brake shoe which engages the first brake disc. 
     
     
       13. A drawing head as set forth in claim 9, wherein the first locking means comprises a first bearing disc having at least one locking slot on its circumference and a locking element is provided in the plane of the base plate which releasably engages the locking slot for halting the bearing means and spacing ring with respect to the base plate. 
     
     
       14. A drawing head as set forth in claim 13, including transmission means which operate the locking element and the brake shoe, and the gripping handle operates the transmission means. 
     
     
       15. A drawing head as set forth in claim 1, wherein the bearing means has second braking means comprising a second braking disc for retaining the straightedge support relative to the bearing means and the spacing ring, and a second brake shoe which presses the second braking disc against the straightedge support. 
     
     
       16. A drawing head as set forth in claim 15, wherein the second brake disc is located between the intermediate thrust disc and the straightedge support. 
     
     
       17. A drawing head as set forth in claim 15, wherein the second brake shoe is displaceably mounted substantially parallel to the bearing axis, and the intermediate thrust disc has a thickness such that the spacing between the base plate and the straightedge support radially outwardly of the starting disc is sufficient to accommodate the second brake shoe which engages the second braking disc. 
     
     
       18. A drawing head as set forth in claim 15, wherein the second locking means further comprises a second bearing disc having at least one locking slot on its circumference, and a locking element is positioned in the plane of the straightedge support which releasably engages the locking slot for stopping the straightedge support with respect to the bearing means and the spacing ring. 
     
     
       19. A drawing head as set forth in claim 18, including transmission means which operate the locking element and the brake shoe, and the gripping handle operates the transmission means. 
     
     
       20. A drawing head as set forth in claim 1, comprising in addition a thrust disc being provided at the bearing means for axially supporting the bearing means against the base plate, and which extends radially outwardly between the base plate and straightedge support. 
     
     
       21. A drawing head as set forth in claim 1, wherein the spacing ring includes radial graduations.